Patient-Reported Outcomes after Surgery for Pigmented Villonodular Synovitis in the Knee: A Cohort Study

Pigmented villonodular synovitis (PVNS) is a rare neoplastic proliferation of large joints, including the knee, with both localized PVNS (LPVNS) and diffuse PVNS (DPVNS) types. DPVNS is known to recur at a higher rate following resection; however, there is little evidence comparing patient-reported outcomes (PROs) between the two types. The purpose of this study was to compare PROs between patients with LPVNS and DPVNS involving the knee 2 years after surgical resection. We hypothesized that DPVNS would have worse 2-year PROs than LPVNS.Sixteen patients who underwent arthroscopic resection of pathology-confirmed PVNS involving the knee were enrolled in a prospective registry. Several PROs, including six Patient-Reported Outcomes Measurement Information System (PROMIS) domains and the International Knee Documentation Committee (IKDC) Subjective Knee Form, were assessed at baseline and at 2 years postoperatively. Mean scores between LPVNS and DPVNS groups were compared using a Wilcoxon exact test, while categorical variables were compared using a Fisher's exact test.Eleven patients (seven LPVNS and four DPVNS) completed both the baseline and 2-year PRO surveys. There were no significant differences in the demographic variables between groups, including age, body mass index, or prior surgical history (p < 0.05). There was a trend toward higher mean PRO scores in the DPVNS group at 2 years postoperatively in all measures, despite lower reported baseline levels of activity as measured by Marx Activity Rating Scale (26.3 vs. 76.7, p = 0.02). The DPVNS group also trended toward more improvement in PROMIS Physical Function (9.7 vs. -2.7), PROMIS Pain Interference (-9.0 vs. -2.5), PROMIS Anxiety (-5.4 vs. -4.4), and IKDC (26.7 vs. 18.9). However, these differences did not reach statistical significance (p < 0.05). There were two recurrences in the DPVNS group and none in the LPVNS group.Patients with knee DPVNS do not report worse outcomes 2 years after arthroscopic resection compared with LPVNS patients.